Hopes that the 44 crew of a missing Argentine submarine might still be alive have been dashed after the navy said an event consistent with an explosion had been detected.

The "abnormal, singular, short, violent, non-nuclear event" was recorded in the south Atlantic by a nuclear test watchdog last week.

Relatives of the missing crew reacted with grief and anger at the news.

It follows a US report of a loud noise in the same area.

The ARA San Juan disappeared last Wednesday. More than a dozen countries including the US, Russia and the UK have sent assistance.

Footage of relatives collapsing to the pavement as uniformed navy servicemen embraced each other was broadcast on live television, sending shockwaves across Argentina.

A huge sea and air hunt is being conducted for the San Juan, a German-built, diesel- and electric-powered submarine that was launched in 1983.

Some relatives have questioned authorities for letting the crew navigate on an aging submarine - criticism that has highlighted the armed forces’ dwindling resources since the end of a military dictatorship in the 1980s.

Authorities have said the level of maintenance, not the age, was what mattered, and that the vessel was in good condition.

It received a midlife upgrade in 2009 in which its four diesel engines and electric propeller engines were replaced, according to the specialist publication Jane’s Sentinel.